Rishi Sunak has been urged to order an investigation into claims Alister Jack broke the Ministerial Code in a lobbying row over a £150m “enhanced investment zone".

The SNP’s Tommy Sheppard has written to the Prime Minister asking the allegations be passed on to the Cabinet Office and Sir Laurie Magnus, the Independent Adviser on Ministers’ Interests.

If the Scottish Secretary is found to have breached the code he may be forced to make some form of public apology, or he could lose his ministerial salary for a period of time, or he could even be expected to offer his resignation.

READ MORE: Alister Jack accused of 'clear breach' of ministerial code

Mr Sheppard’s call follows a report in The Herald on Sunday that the Scottish Secretary used his position as a minister to lobby for Stranraer and Cairnryan in his Dumfries and Galloway constituency to be part of the new low tax, low regulation area for Northern Ireland, announced by the UK Government last week.

Mr Jack revealed the extent of his involvement in the deal during his appearance before the UK Covid Inquiry last week.

It came in response to a question about how the salient details of conversations were recorded in the corporate record of the UK Government.

He said: “When I conduct business, I inform my office.

"So, for instance, in the last ten days I have had conversations with the Secretary of State for Northern Ireland directly about including Stranraer and Cairnryan in an investment zone for Northern Ireland, as we move towards Stormont hopefully being up and running again.”

He continued: “And I had a conversation with Jeffrey Donaldson and I then came back to speak to my office directly and inform them that I'm trying to have Stranraer and Cairnryan included in an investment zone for Northern Ireland - because it's not possible to do a free port structure - and they then take that information and go back, officials to officials, whether it's in the [Department for Levelling Up, Housing and Communities] or the Northern Ireland Office, in this case - both DLUHC and Northern Ireland - so investment zones are DLUHC, in Northern Ireland Office - obviously regarding the negotiations.

"They then go back and cement what I, what we, what I think we have agreed."

Mr Jack was also praised for his work in securing the inclusion shortly after it was announced, with a UK Government source telling the press that the minister had "been the driver behind this exciting proposal which will strengthen Scotland’s economic ties with Northern Ireland and benefit the whole United Kingdom".

Section 1.3 (h) of the ministerial code states: "Ministers in the House of Commons must keep separate their roles as minister and constituency member".

Section 6.4 goes on to say that “where ministers have to take decisions within their departments which might have an impact on their own constituencies, they must take particular care to avoid any possible conflict of interest".

It also calls on ministers to “advise their Permanent Secretary… of the interest and responsibilities should be arranged to avoid any conflict of interest".

In his letter to the Prime Minister, Mr Sheppard who shadows the Scottish Secretary in the Commons, said this “appears to be a clear breach of the Ministerial Code".

He added: “I therefore request that you immediately ask the Cabinet Office to investigate the facts of the case and/or refer the matter to the Independent Adviser on Ministers’ interests.”

The Herald: SNP MP Tommy Sheppard is taking the UK Government to court over its secret Union polling

Mr Sheppard told the Herald: “The Prime Minister must open an investigation into whether the Secretary of State for Scotland has broken the Ministerial Code without delay, and pass the information across to the Independent Advisor on Ministers interests.

“Mr Jack’s comments during the Covid-19 Inquiry clearly show that he used his position as a minister to influence the enhanced investment zone for his constituency, which flies in the face of the Ministerial Code.

“However, this is something we’ve become accustomed to with this UK Tory government. Whether they’re handing out contracts worth millions of pounds for defunct PPE, or stuffing the House of Lords with their cronies and donors, their rank hypocrisy is clear for all to see.”

A UK Government spokesperson said: “Alister Jack was acting in his capacity as Secretary of State for Scotland.

"The NI/Stranraer Investment Zone would be a huge boost to jobs and the economy of southwest Scotland, strengthening Scotland’s economic ties with Northern Ireland and benefitting the entire of the UK.”

Details of the new investment zone were announced in the UK Government's Safeguarding the Union command paper published last week. The document set out a number of new initiatives to try and restore the devolved government in Northern Ireland.